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**Graphene -- Green's function technique**

Hi,

I am looking for a comprehensive review about using Matsubara Green's function technique for graphene (or at least some hints in the following problem). I have already learned some finite temperature Green's function technique, but only the basics.

What confuses me is that graphene has two sublattices (say A and B), and so (in principle) we have four non-interacting Green's functions: [tex]G_{AA}(k,\tau)=-\langle T_{\tau}a_k(\tau)a_k^{\dagger}(0)\rangle,[/tex] ,

where [tex]a_k[/tex] is the annihilation operator acting on the A sublattice. G_{AB}, G_{BA} and G_{BB} are defined in a similar way.

Of course, there are connections between them, but G_{AA} and G_{AB} are essentially different. Now when I am to compute e.g. the screened Coulomb potential, I do not know, which Green's function should be used to evaluate the polarization bubble.

Thank you for your help!